KWARTAND BLAZER
2726 J . Org. Chem., Vol. 36,No. 8, 1970
Analysis of Mass Spectral Fragmentation Patterns in Various Bicyclic Alcohols HAROLD KWARTAND THOMAS A. BLAZER Department of Chemistry, University of Delaware, Newark, Delaware 19711 Received December 13, 1969 Various bicyclo[2.2.1] heptyl, bicyclo[2.2.2]octyl, and bicyclo[3.2.1]octyl substrates, particularly alcohols and olefins, have been subjected to careful study of their fragment ions occurring in the high-resolution mass spectrometer. The olefins undergo retro-Diels-Alder cleavage as the principal mode of fragmentation. An internal retro-Diels-Alder18 fragmentation appears to take place in the [3.2.1]octene ion which does not accommodate a normal class D fragmentation. All the alcohols, including the bridgehead cases, undergo dehydration via the formation of an intermediate carbonium ion, which then experiences extensive scrambling of the hydrogen (and deuterium) atoms on the skeleton before completing elimination of the elements of water. The resulting olefin ion then suffers a retro-Diels-Alder fragmentation, but this route is shown to be vitiated as a means of locating the deuterium on the skeleton and tracing the course of rearrangement reactions in solution thereby. It is demonstrated, however, that the m/e 57 peak may be applied for this purpose since it is produced in all bicyclic alcohol cases without rearrangement of the skeleton in the mass spectrometer. The manner in which m/e 57 (and m / e 58 in deuterated cases) arises through fragmentation, the method of locating H and D in bicyclic models, and its use in tracing the course of solvolytic rearrangements are discussed in detail.
Recent studies of carbonium ion rearrangements of bicyclo [3-2.11-Boctanol and bicyclo [2.2.2]-2-octanol sulfonate esters and analogous derivatives’b required application of the mass spectrometer as a means of following the course of reaction. Since more information was needed concerning the fragmentation patterns of bicyclic alcohols, a study was undertaken of the electron-impact fragmentation of 1, 2, and 3 alcohols, the olefins derivable therefrom, and related compounds.
OH
2
6
X
OH 2
1
X
=
3
3
hydrogen (normal) or deuterium
I n each instance the occurrence of HzO elimination producing an olefin ion was confirmed by the observation of a metastable peak in the mass spectrum. Two general fragmentation paths were observable, one originating from the parent alcohol and directed by the oxygen containing fragment, the other stemming from the olefin and directed by the double bond. Results and Discussion Molecular ions. -The
parent peaks of the alcohols
(1, 2, 3) were always readily perceived. They ranged from a low of 1.7% for 1 to a high of 21.5% for 3.
As expected, the corresponding olefins exhibited more intense molecular ion peaks; e.g., 14.7% for bicyclo[2.2.2]octene vs. 7.1% for the alcohol 2. Other investigators have shown2~3 that in the case of monocyclic alcohols the molecular ion is more intense in the case of equatorial hydroxyl than axial. Such differences, however, though significant in a relative sense, do not appear to be large on an absolute scale. From a practical viewpoint, this did not seem to offer a solution to our (1) (a) H. Kwart and K. King, Cham. Rev., 68, 415 (1968). (b) H. Kwart and J. L. Irvine, J. A m e r . Chem. SOC.,91, 541 (1969). (2) K.Biemann and J. Seibl, ibid., 81, 3149 (1969). (3) D. R.Dimmel and J. Wolinsky, J. Org. Chem., 38, 410,2735 (1967).
problem and no attempt was made to study epimeric differences of this nature. Retro-Diels-Alder Fragmentations. -This type of mechanism is know to operate in cyclohexenes. Biemann4refers to this as a “class D” mechanism and lists two requirements for the operation of the fragmentation mode: (1) the presence of a cyclic olefin or similar system, and (2) the absence of other bonds which might clleave with particular ease via certain stated mechanisms. Since bicyclo [2.2.1]-2-heptene (4) and bicyclo [2.2.2]-2-octene (5) could be prepared via DielsAlder reactions, and since the normal (X = H) alcohols 1 and 2 could dehydrate under mass spectral circumstances t o form these olefins, it was assumed that evidence for a retro-Djels-Alder reaction might be found in the mass spectra of 1 , 2 , 4 , and 5. The peaks corresponding to this “class D” mechanism actually constitute the major fragment ions of the mass spectra of 4 and 5 (see Figure 1). This observation holds for the spectra obtained at 15 V as well as those obtained at the conventional 70 V. Metastable transition peaks representing these fragmentations were observed at m/e 46.3 in the spectrum of 4 and at m/e 59.5 in the spectrum of 5 . The (normal) alcohols 1 and 2 also show evidence of the retro-Diels-Alder fragmentation. The peaks analogous to those in the spectra of 4 and 5, although not the major. peaks of the spectra (see Figures 2 and 3) , are still very intense, 20.1% for the m/e 66 peak in (normal) 1 and 79,0% for the m / e 80 peak in (normal) 2. I n addition, these alcohols also display metastable transition peaks at m/e 46.5 in the case of (normal) 1 and m/e 59.4 in the spectrum of (normal) 2. A metastable peak at wz/e 60.2 in the spectrum of the deuterated (X = D:i 2 confirm this fragmentation. This results from the tsansition 109 --t 81 28. On the other hand, n o metastable peak was detected in the mass spectrum of the [3.2.1] (normal) alcohol 3 (see Figure 4) which could be correlated with fragmentation via a “class D” pathway. This is attributable to the absence of structural accommodation for the retro-
+
(4) K.Biemann, “Mass Spectrometry, Organic Chemical Applications,” McGraw-Hill Book Co., Inc., N. Y.,1962. See also, for further illustrations of the RDA fragmentation in bicyclic compounds, T. Gato, et al., Tetrahedron, 22, 2213 (1966),and W. C.Steele, B. H. Jennings, G. L. Botyos, and G. 0. Dudek, J. Org. Chem., 80, 2886 (1965).
MASSSPECTRAL FRAGMENTATION PATTERNS IN BICYCLIC ALCOHOLS J. Org. Chern., Vol. 35, No. 8,1970 2727 I
1081
41 27
93
39
109
(b)
67
41
80
27
80
54
39
94
58 15
,
I
Ill
Ill
II
I
It
I27
1
(PI I
67
41
27
Figure 1.-Mass
spectra: (a) bicyclo[2.2.1]-2-heptene(4), (b) bicyclo [ 2.2.21-2-octene(5).
1
94
66
I5
II
Figure 3.-Mass
I
54
39
95
7 111
I
I
II
128 (PI
spectra: (a) bicyclo[2.2.2]-2-oct;anol(2, X = = D); (0) bicyclo-
H);(b) bicyclo[2.2.2]-2-octanol-2-d(2, X [2.2.2]-2-octanol-3,3-dt (7).
68
39 41 27
57 53
15
I
II
I
83
I
1
I
(bl 85
I
951
39
79 8 0
41
27
58 53
15 I
1
84
1
I13
(PI
Figure 4.--ldass spectra: (a) bicyclo[3.2.1]-2-octanol(3); (b) bicyclo [2.2.2] -1,8-octadiol (IO).
readily under far less energetic circumstances than prevail in the mass spectrometer (as illustrated below).
(one or
m/e 126
more steps)
m/e 108
Figure 2.-Mass spectra: ( a ) bicyclo[2.2.l]-2-heptanol,endo (1, X = H); (b) bicyclo[2.2.1]-2-heptanol,exo; (c) bicyclo[2.2.1]-2-heptanol-2-d1 endo (1, X = D); (d) bicyclo[2.2.1]-2heptanol-3,3-dz,endo (6).
Diels-Alder reaction^.^ However, a major peak (98.7%) was recorded at m/e 80 whose constitution was established to be COBs+(through high-resolution mass determination). This could arise as a result of fragmentation via an internal retro-Diels-Alder,6 a well characterized electrocyclic rearrangement proceeding (5) See, for a full disoussion of this reaction, ref la.
Dehydration.-The major peak in the spectra of the bicyclic alcohols 1 and 2 and their deuterated analogs is due to the loss of water, I n the mass spectrum of the [3.2.1] alcohol, 3 (X = H), the peak due to the loss of a mole of HzO, although not the major peak of the spectrum, is still very intense (32.6%). Metastable transition peaks establish this fragmentation as due to
2728 J . Org. Chem., Vol. 36, No. 8,1970
dehydration, since the 18 mass units are lost as a single group. The loss of water has been demonstrated to occur to varying extents in the spectra of monocyclic alcohols, ranging from approximately 10% in cyclopentanol to 50% in cyclohexanol. Dehydration by way of aldehyde intermediates, which have been shown to fragment with subsequent elimination of water, has been suggested6 as one possible mechanistic course. However, this path is not functional in any of the bicyclic alcohols under study here. No evidence could be found to confirm the fragmentation of a formyl group from the parent ion. I n the case of cyclohexanol, the source of the hydrogen which coupled with the hydroxyl group (comprising the water eliminated) was proven’ to be distributed around the ring with the exception of the CI. The failure of the hydroxyl-bearing carbon to yield its other hydrogen to form the water eliminated has been confirmed by our studies. In the spectra (c), Figure 2, of alcohol 1 (X = D) and (b), Figure 3, of 2 (X = D) there is no evidence for the loss of 19 mass units, which could occur if this atom were involved, (HDO in these cases). The source of the second hydrogen could have been the C3 if the analogy to an a#-elimination reaction in solution is fulfilled. The resulting olefin (for example, the bicyclo[2.2.1] heptene ion) could then give rise to a retro-Diels-Alder fragmentation route, as discussed in the previous section of this report. However, when endo bicyclo [2.2.1]-2-heptanol-3,3d2, 6, suffers fragmentation, as is evident from the spectrum (d), Figure 2, the m/e 96 (the base peak) is more than ten times as intense as m/e 95, indicating
KWART AND BLAZER (as pointed out earlier) are very evident in the spectra of the (normal) alcohols 1 and 2. In the case of 7 , the m/e 80, representing the expulsion of CD2=CH2 from the base m/e 110, is significantly more intense than m/e 81 and 82 (corresponding, respectively, to the expulsion of CHD=CH2 and CH2=CH2). Consequently, the structure 9 can be assigned as the preponderant olefin (ion) resulting from dehydration of 7. Its formation could be readily accomplished in two successive steps involving C-H bond breaking in the intermediate carbonium ion 7a (illustrated below).
7a
I
relro Diels-
Alder
m/e 80
A concomitant path of more than equal likelihood producing expulsion of CDFCH~ from the intermediate carbonium ion 7a is the result of very facile rearrangement to the [3.2.1] ion (or its nonclassical equivalent). As indicated earlier, the occurrence of an internal retro-Diels-Alder5 is a highly probable fragmentation mode, which in the present instance can also account for the observed results (illustrated below).
+ m/e 110 6
7
that little or no a,p elimination of deuterium has taken place. This confirms an observation briefly reported earlier.* Moreover, we have found a nearly identical result in the case of fragmentation of the corresponding [2.2.2]bicyclic alcohol 7, where the base peak (m/e 110) is actually more than twenty times as intense as the peak (m/e 109) corresponding t o HDO elimination. Clearly, the loss of hydroxyl from the parent ion in each case (6 and 7) has resulted in a carbonium ion in whose structure hydrogen and deuterium positions have become extensively scrambled. Presumably this has occurred through very rapid C-C bond shifting and hydride migrations such as are characteristic of the similarly structured carbonium ions in so1ution.l Ultimately these carbonium ions must lose hydrogen and be converted t o the olefin ions 8 and 9. This is demanded by the retro-Diels-Alder products of fragmentation of 8 and 9, namely, the formation of cyclopentadiene (m/e 66) and cyclohexadiene (m/e 80) ions (respectively) , through expulsion of a neutral ethylene fragment, which (6) J. A. Gilpin and F. W. MoLafferty, Ana2. Chem., 29, 990 (1957). ( 7 ) P. Natalis, Bull. Soc. Rou. Sci. Lieee, ai, 790e (1962). See also C. G. MacDonald, J. S. Shannon, and G. Sugowdz, Tetrahedron Lett., 13, 807 (1963). (8) W. Benr and K. Biemann, J . A n e r . Chem. Soc., 86, 2375 (1964).
1
m/e 110
The mechanism is supported by the fragmentation pattern of the monodeuterio alcohol (2, X = D) (see spectrum b, Figure 3), where the ratio of m/e 109/80 is nearly identical with the ratio of m/e 110/80in the spectrum of 7. Furthermore, the ratio of m/e 80/79 is almost the same for the deuterated alcohols 2 (X = D) and 7, but is significantly different for the undeuterated bicyclooctanol shown in spectrum a, Figure 3. Unfortunately, it is not possible to trace with the same degree of confidence (as in 7) the course of rearrangement in the corresponding carbonium ion intermediate formed from 6 . The cyclopentadiene ion (C,H6+) derived from alcohols is accompanied by a strong (e6&)+ peak and both of these appear to experience extensive protonation (to m/e 67 and 68, re-
MASSSPECTRAL FRAGMENTATION PATTERNS IN BICYCLIC ALCOHOLS J . Org. Chem., Vol. 36, No. 8, 1070 2729 spectively; see Figure 2) in contrast to the same ion (m/e 66) arising from the bicycloheptene directly (see spectrum a, Figure 1). I t will be seen, nevertheless, that the m/e 66 derived from 6 is of slightly greater intensity than m/e 67 and 68, whereas the converse is true of the undeuterated norborneols in Figure 2 (spectra a and c). This would suggest that hydride migration in the carbonium ion derived from 6 through loss of hydroxyl is somewhat more facile. That is to say, this carbonium has a sufficiently greater lifetime than that arising from 7,allowing for a greater extent of hydride migrations and producing 8, a more extensively scrambled structure than 9 (as is shown below in classical ion notation),
&: e+&; t
migration
111
Ill
I-. 8 [retro Diela-Alder
0 m./e 66
f
CDz=CHz
+
0+
83 +57
CHz==CH2
m/e 68
& --+&
+ 26 (m* -39.1)
84 +58 f 26 (m* -40.1)
A parallel observation of the relative lifetimes of these carbonium ions in soIution and the significance of this factor in determining the occurrence of C-C and C-H bond migrations have been previously discussed.l Finally, the case of the bridgehead diol 10 will serve as an illustration of the generality of dehydration, even where CY,^ elimination of the elements of water is most unlikely because the resultant ion would possess the highly &rained bridgehead double bond. Nonetheless,
HO
Formation of m/e 57 peak.-Another mode of stabilizing the odd-electron molecular ion of an alcohol (supposedly formed by expulsion of a nonbonding electron of an oxygen atom) is through rupture of the Cz-C3 bond with subsequent decomposition to an m/e 57 ion and a hydrocarbon radical. High resolution mass measurements on the bicyclic alcohols studied in this investigation established that the fragment ion of mass 57 has the composition (C3HsO) +, probably a resonance stabilized ion of the form [CHpCHCHOH]+. This is in accord with a conclusion reported earlier’vg for cyclohexanol and cyclopentanol. Although m/e 57 is not the major peak of any of the bicyclo alcohols studied here, it is quite intense, comprising 28.6% in 1, 22.7% in 2, and 43.9% in 3. These are shifted to m/e 58 in the deuterated analogs with similar peak intensities for corresponding substrates, (i.e.>where W = D replaces X = H). Dimmel and Wolinsky3 have reported m/e 57 as the ninth most intense peak in the spectra of both endo- and exo-norbornanol. Appropriate labeling of the [2.2.1] and [2.2.2] alcohols established that the initial fragmentation steps in the formation of m/e 57 from these alcohols involves the rupture of the Cz-C3 bond. Thus, deuteration of the hydroxyl-bearing carbon in each case shifted the peaks to m/e 58, but complete deuteration of the CY (C3) carbon produced no shift of m/e 57. Additional evidence bearing on the course of fragmentation are the metastable peaks at m / e 38.9 (calculated 39.1) in the spectrum of the bicyclic alcohol 2 (X = H), and at m/e 39.9 (calculated 40.1) of deuterated 2 (X = D). Calculations indicate further that these could be the result of fragmentations which yield peaks at m/e 57 and 58, respectively (illustrated below).
f HzO
\
a prominent P - 18 peak is noted in the spectrum (b, Figure 4) of 10. Similarly the ion product of subsequent retro-Diels-Alder cleavage in the form of the relatively intense peak (24%) at m/e 96 is identifiable by high resolution mass determination as (C6HsO) +, and its deprotonated satellite (m/e 95, 21%). These data can (once again) be reconciled with the occurrence of hydride migration following the formation of the (unst,ablc) bridgehead ion through loss of hydroxyl.
This would require that there be a prior fragmentation splitting off 43 mass units. Evidence for this occurrence can be found in metastable peaks present in the spectra of 2 (both X = H and X = D). 126 +84
+ 43 (m* observed 54.7, calculated 5 4 . 7 )
127 -+- 84
+ 43 (m* observed 55.6, calculated 5 5 . 6 )
-
On the basis of these lines of evidence the most likely fragmentation path (2a 2f) which can be proposed for the bicyclooctanols is that displayed in Scheme I where encircled H traces the hydrogen retained in m/e 57. An analogous fragmentation route (la --t le) can be plotted for formation of m/e 57 from the bicycloheptanol 1 (see Scheme 11) where encircled H traces the hydrogen retained in rn/e 57. An alternative route leading from 1b + l g (Scheme 111) upon rupture of the Ca-C8 bond is one of the (9) H. Budzikiewicz, C. Djerassi, and D . H. Williams, “Interpretation of Mass Spectra of Organic Compounds,” Holden-Day, Inc., San Francisco, Calif., 1984.
2730 J . Org. Chem., Vol. 96,No. 8, 1070
KWART AND BLAZER
SCHEME I
0
0
2
2a
2b
SCHEME I1
1
lb
2c
U
IC
Id
2f 2d
la
le
2e
A+ (43 mass units)
m/e 57
cleavage
m/e51
1
strongest competitors for fragmentation of the parent (along with the dehydration mechanism previously considered). The m/e 67, one of the most intense peaks aside from P - 18 in the spectra of all the alcohols in Figure 2, has been shown by high-resolution mass determination to be the pure hydrocarbon ion (C5H7) +. The fact that this peak is equally intense in the spectra of all the bicyclo [2.2.1Iheptanols, both deuterated and nondeuterated [l (X = H), 1 (X = D), and61 may be cited as strong evidence supporting this mechanistic proposal. It will also be recognized (see following section of this report) as one of the factors vjtiating the application of the retro-Diels-Alder cleavage for locating deuterium on the norbornyl skeleton via the m/e ratio 66 :67. The complete generality of this overall cleavage course in bicyclic alcohol fragmentations leading to m/e 57 is t o be perceived in the spectrum of the bridgehead diol 10. In all other (mono) alcohols studied the m/e 57 retains the charge [because it has the electronegative oxygen in its (C3H50)+ structure] while losing neutral hydrocarbon fragments in the final cleavage steps. I n the diol 10, however, we observe that the second (hydroxyl) oxygen tends to stabilize the ionic charge, with the consequence that both cleavage fragments can be readily identified as intense peaks; the m/e 57 peak is 22% and the m/e 85, identified as (C5HsO)+, is the most intense (base) peak in the mass spectrum (b), Figure 4. The following (Scheme IV) appears to be the most attractive way of accounting for this result, in consonance, as well, with the fragmentation patterns of the other bicyclic alcohols considered in these studies. Applications to Deuterium Analysis in Atom-Bridged Compounds.-The migration of deuterium and rearrangement of the carbon skeleton which might be associated with Wagner-Meerwein rearrangements
cleavage
SCHEME I11
-CHJ'
lb
If
&OH
H.
can be followed in certain cases by examination of some of the fragment ions in the mass spectrum. For example, Cristol and coworkerslO have demonstrated that the retro-Diels-Alder decomposition of dehydronorbornyl acetates provides a way of determining the location,of deuterium on the skeleton of this class of bicyclic derivatives. Essentially the method consists of a comparison of the intensities of m/e 66 and 67 peaks for estimating the extent of deuterium migration into that part of the molecule which acquires the cyclopentadienyl ion structure in fragmentation of the parent ion. We have attempted t o apply this approach t o (saturated bicyclic) norbornyl derivatives which would undergo elimination of HX in the spectrometer. Since fragmentation of the (P - HX) peak to retro-DielsAlder products is a common occurrence, it seemed likely that a method of deuterium tracing analogous to that used for dehydronorbornyl derivatives could be ap(10) S. J. Cristol, R. A. Sknchez, and T. C . Merrill, J . Ore. Chem., 81, 2738 (1966).
MASSSPECTRAL FRAGMENTATION PATTERNS IN BICYCLIC ALCOHOLS J. Org. Chem., VoZ. 35, No. 8, 1970 2731 SCHEME
IVa
3 intramolecular
m/e 85 0
HO
(X) denotes three equivalent ways in which this, fragmentation would occur.
plicable. However (as has been shown earlier in this article), the loss of HOH in the bicyclic alcohols studied was not a simple a,p elimination. Instead, a deep seated rearrangement (in the intermediate carbonium ion) of the hydrogen (and deuterium) atoms of the skeleton attended the loss of hydroxyl. This circumstance clearly obviated the use of any fragment ion which did not contain hydroxyl for purposes of locating deuterium atoms on the skeleton of any saturated bicyclic derivative, particularly the alcohols. Furthershown in the previous section Of this report, the m/e 67 peak arises from One Of the most abundant ions in the spectra of norbornyl alcohols independently of deuteration in the czand C Bpositions. This must surely be the most decisive reason why the retro-DielsAlder cleavage cannotbe applied for structuretracing in saturated norbornyl derivatives. Clearly, then, the only fragment peak which could be used reliably for such trace analysis is one containing the hydroxyl (thereby avoiding the rearrangements stemming from loss Of hydroxy1)* The m / e 57:58 ratio fulfills this Specification, both for the bicyclo[2.2.1] and - [ 2 . 2 . 2 ]alcohols. The substitution of deuterium for the hydrogen on Cz in each case shifts the bulk of this peak to 58, Thus, if, as result of reaction,the D is "scrambled" out of the C2or Cs positions, this event can be readily detected in all rearrangements of norbornanol derivatives (where the product can be converted to a norbornanol sample for mass spectral analysis). However, in this to rearrangementS Of bicyclo [2.2.2]OCtanOlderivatives' a StatiStiCaI correction of two must be made for the equivalence of the caand positions in fragmentation. This can be readily Seen in the following illustrative computation, Here the m/e 57 58 in a nondeuterated sample corresponds t o 100% migration of the deuterium from Cz while the same measured ratio of 57 :58 intensities in the known deuterated, alcohol mould represent no deuterium migration from Cp. Thus, the nondeuterated sample of 2 ( = 100% D loss) shotved a 7.7 (m/e 57158) ratio, while in a sample of 2, deuterated only at cZ( = 0%. - D loss), the measured ratio %'as 0.22, In a typical acetolysis of the brosylate derivative of the
c,
m/e 57
sample deuterated at Cz the acetate product was purified by glc methods and saponified, and the pure [2.2.2] alcohol recovered in which some of the deuterium had migrated from Cz. The measured ratio of this product was 0.28. This result calculates as 2
[7 . 7o'28 - 0.22]
=
6% D migration
Experimental Section Technique.-The mass spectra of most of the compounds were obtained on a Consolidated Electrodyllamics carp. instrument, Model 21-103-C. Most of the high-resolution fragment ion mass determinations were carried out with a Model 11Q instrument. Sample introduction was effected by means of a 350' capacity heated inlet accessory unit. Sufficient volatility of all samples used was realized at inlet temperatures in the range of 150'. The spectra were obtained usually employing nominal 70-eV ionizing energies except as noted for low voltage spectra where 15-eV ionizing energies were used. The ionizing current could always be adjusted t o yield spectra of satisfactory intensity. Origin of Samples.-We are indebted to John L. Irvine for furnishing the bicyclo[2.2.2]octano1 samples (2, X H and = D). The samples of 6 and 7, the bicyclic alcohols dideuterated at Cs,were kindly prepared by Dr. Norbert Kucharczyk from the corresponding ketones by three successive base-catalyzed exchanges in dioxane-Dg0 media, followed by lithium aluminum hydride reduction t o the alcohol, and purification of the product = H and = D) by familjar methods, The samples of were prepared by reduction of the norbornanone using lithium aluminum hydride or deuteride, respectively, adapting the procedures by Brown." Gas chromatographic cuts were ordinarily used to obtain the appropriate mass spectra. The structures of the alcohols and the positions of deuteration, where possible, were always confirmed by nmr and ir analysis. The samples of bicyclo[2.2.1]-2-heptene(4) and bicyclo[2.2.2]2-octene ( 5 ) were obtained from Chemical samples co., COlUmbus, Ohio, and were recommended to be greater than 99% purity. The sample of bicyclo[2.2.2] -1,%octanediol was kindly furnished (in pure form) by Dr. James Kauer. Xass spectra were taken on these samples as received.
x
(x
x
(x
No.-1 (x = 497-36-9; D), 24867-16-1; 2 (X = H), 24848-12-2; (x = D), 5602-48-2; 4, 498-66-8; 5 7 24867-06-9; 3 (X = 931-64-6; 6, 10503-54-1; 7, 24867-10-5; 10,24867-"6; bicyclo[2.2.11-2-heptanol,exo,497-37-0. (11) w. G . Brown, erg. React., 6,469 (1951). H)j
